Characterization of the intergenic region which regulates the MspI restriction-modification system.

摘要

The 110-bp intergenic region between mspIM and mspIR, the genes encoding the MspI modification (M.MspI) and restriction (R.MspI) enzymes, respectively, was fused, in both orientations, with lacZ. Expression of a single-copy mspIM-lacZ fusion is more than 400-fold stronger than expression of an mspIR-lacZ fusion. M.MspI in trans represses expression of the mspIM-lacZ fusion by binding to the DNA but does not affect expression of the mspIR-lacZ fusion. Transcription start sites of the genes were identified, and a set of nonoverlapping promoters was assigned. DNase I footprinting showed that M.MspI binds to a site within the intergenic region that includes only the mspIM regulatory elements.